Improved polymethine sensitizing dyes



United States Patent 3,156,685 IMPRG'VED PQLYMETHINE SENSETEZING EYESJean Mm'ie Nys and Henri Depoorter, Mortsel-Antwerp, Belgium, assignorsto Gevaert Photo-Frodueten N.V., Mortsel, Belgium, a Belgian company NoDrawing. Filed July 3, 1961, Ser. No. 121,372 Claims priority,application Great Eritain June Ztl, 1957 5 Claims. (Cl. 260--240.6)

This invention relates to new methine dyes and to their preparation anduse as sensitizers for photographic silver halide emulsions, and tomethods of sensitizing such emulsions by means of such sensitizing dyes.

A great number of methine dyes are known and many of them have beenfound to sensitize photographic emulsions in a variety of usefulmanners. These sensitizing methine dyes, however, when used in suchemulsions leave in general a residual stain in the colloid image-bearinglayers and/ or in other photographic layers such as sublayers or even inthe film support of developed and fixed photographic elements. Thestaining eifect is particularly troublesome in the case of photographicelements which are used in photo-mechanical processes, for examplephotographic negatives of the lithographic type which are to becorrected subsequently by a color mask image, and therefore a neutraltint is an absolute requirement. This staining effect is furthermoreparticularly objectionable in photographic papers since it isimpossible, when such dye-sensitized emulsions are used, to obtainbright whites in a black-and-white picture or a true reproduction of thecolors in a color picture. A light rose or yellow residual stain mayfurther cause trouble when a finished photograph is exposed partly tofull daylight, the other part being covered, so that under the influenceof light the residual dye-stuff can bleach out, leaving an image whichis partly white and partly colored.

It is therefore very important, when sensitizing photographic emulsionsby dyes, to avoid this residual straining effect in finishedphotographic papers, in films of the lithographic type or in otherfinished photographs in which such stain is objectionable.

It is an object of the present invention to provide a new class ofmethine dyes which do not leave a residual strain in developed and finedphotographic elements. A further object is to provide methods forpreparing these new dyes. Still another object is to provide silverhalide emulsions sensitized with these new dyes. A still further objectis to provide a practical and useful method for sensitizing silverhalide emulsions which has the great advantage that, when such emulsionsare coated on a suitable support, the exposed photographic element afterdevelopment and fixing gives a finished photograph which is essentiallyfree from any residual stain. Other objects will become apparent from aconsideration of the description and examples.

It is common knowledge thatthe methine dyes are adsorbed on the silverhalide crystals and on the particles of the colloid binder along theorganic residue attached to the auxochrome nitrogen atom, that is thecyanine nitrogen atom which is linked through a conjugated carbon chainto another auxochrome group such as for example a nitrogen atom or acarbonyl, thiocarbonyl or cyano group.

It has now been found that sensitizing methine dyes, which are adsorbedon the silver halide crystals and on the hydrophilic water-permeablecolloid binder along an organic residue bearing a hydrophilic group asdefined more particularly hereinafter, do not leave an objectionableresidual stain in the photographic layers after development and fixingof the exposed photographic element has been completed, independently ofthe Watersolubility of the new methine dyes involved. It has been3,156,685 Patented Nov. 10, 1&64

found indeed that by introducing in the molecule of the methine dye anorganic residue containing a hydrophilic group according to theinvention, the residual stain is at all events completely avoided,although in many cases the water-solubility of the new dyes is notmarkedly changed and in some cases even diminished. In this way it wassurprisingly discovered that some new methine cyanine dyes which containan organic residue bearing a hydrophilic group according to theinvention are considerably less water-soluble than the correspondingalkyl substituted dyes, but nevertheless left no residual stain in thefinished photograph. The readiness with which the new methine dyes canbe removed from the exposed photographic element during processingconsequently has no direct relation with the solubility of the dyesinvolved but is or may be regarded as a result of a desorptionphenomenon whereby in aqueous medium the dye molecules are withdrawnfrom the surface of the silver halide crystals and/ or of the particlesof the colloid binder on account of the great water-affinity of theorganic residues containing the hydrophilic groups according to theinvention. The existence of such desorption phenomena is known fromadsorption chromatographic separation techniques where the solubilitydoes not play a preponderant role either.

It is further known that methine dyes containing electro-negative groupsin general are relatively poor sensitizers for photographic emulsions oreven desensitizers for such emulsions and therefore not useful aspractical photographic sensitizers.

It has now been found that the sensitizing power of the new methinedyes, which contain an organic residue bearing'a hydrophilic groupaccording to the invention, is not markedly reduced notwithstanding thehigh electronegative value of the hydrophilic groups involved.

We have also found that the introduction into a methine dye of such anorganic residue bearing a hydrophilic group as defined more particularlyhereinafter clearly results in a shifting of the sensitization spectrumto the shorter wave-lengths and that these hypsochrome shifts can insome cases amount to 510 mg. In the case of orthochromatic emulsionsthis hypsochrome shifting may be very desirable to allow an extension ofthe spectrum composition of the light in the darkroom to physiologicallyclearer, that is shorter wave-lengths without the risk of fogging theemulsion; such an extension is inter alia required when treatingphotographic elements used for copying and/ or photomechanicalprocesses. If this shif ing is undesirable, it can be remedied byadaption of the other elements constituting the methine dye, for exampleby changing a heterocyclic nucleus or by introducing a substituent intoa nucleus or in the conjugated chain.

According to the present invention we provide new sensitizing methinedyes in which at least one heterocyclic nitrogen atom carries an organicresidue of the following constitution:

wherein A and B each represents a hydrocarbon group. That residue linkedto an auxochrome heterocyclic nitrogen atom of methine dye salts mayhave a betaine structure by intra-rnolecular ionization of the sulphonicacid group:

In the above formulae A preferably represents alkylene groups havingfrom 14 carbon atoms such as methylene, ethylene, and propylene alone orcoupled to .a mononuclear arylene radical such as benzylene (phenylenemethylene) and 3 preferably represents an alkylene group having from 1-6carbon atoms such as methylene, ethylene, propylene and butylene.

According to a further feature of the present invention we provide aphotographic silver halide emulsion sensitized by incoiporating thereinat least one of the new methine dyes as hereinbefore defined. Thepresent invention further includes a process for preparing highsensitive photographic silver halide emulsions which give, afterdevelopment and fixing of the exposed photographic element, a finishedphotograph which is essentially free from any residual stain, whichcomprises treating a photographic silver halide emulsion with asensitizing polymethine dye as defined herein and a light sensitivephotographic element containing at least one silver halide emulsionlayer sensitized according to the foregoing process.

The present invention also includes a method of preparing methine dyes,which method consists in treating a quaternary salt of a heterocyclicnitrogen base bearing at the nitrogen atom an organic residue of thefollowing constitution:

wherein M represents an alkali metal atom, such as sodium, potassium orthe like or an ammonium group and A and B have the same significance asset forth hereinbefore, by one of the methods known to be capable ofconverting the alkyl, aryl or aralkyl quaternary salt of suchheterocyclic base into a methine dye. The word known is to be understoodas designating methods in actual use or described in literature on thesubject.

The quaternary salts employed in the present invention can be obtainedby treating the corresponding heterocyclic nitrogen base with a compoundof the general formula:

wherein X represents an acid residue such as for example a halogen atomsuch as Cl and Br, and M, A and B have the same significance as setforth hereinbefore. heterocyclic nitrogen base and the compound ofFormula I above are merely heated together to form the quaternaryhalide. Crude quaternary halides prepared in this manner may beconverted, if desired, into other quaternary salts before employing themto prepare our new methine dyes.

The compounds of the general formula I wherein B represents ahydrocarbon radical containing a straight carbon chain of at least threecarbon atoms may be prepared by heating together a compound of thegeneral formula:

XACO-OM with a compound of the general formula:

wherein B represents a hydrocarbon radical containing a straight chainof at least three carbon atoms and not more than 6 carbon atoms andcontaining preferably 3 or 4 carbon atoms and M, X and A have the samesignificance as set forth hereinbefore.

The compounds of the general formula I above wherein B represents amethylene radical may be prepared by heating together a compound of thegeneral formula:

X-A-CO o X-A-C6 with a compound of the general formula:

HOB 4O OM wherein B represents a methylene radical and X, A and M havethe same significance as set forth hereinbefore. The present applicationis a continuation-in-part of The 4 our application Serial No. 742,713filed June 18, 1958, now abandoned.

The following examples will serve to illustrate the method for preparingthe intermediate compounds of the general Formula I above.

PREPARATION I 3-Br0m0-Acetoxy-Propane-I-Sulphonic Acid Sodium Sail BrCHCOOCH CH -CH SO Na Sodium bromo-acetate (50 g.) and3-hydroxypropanel-sulphonic acid sultone (50 g.) are heated for sixhours at 150 C. upon an oil-bath and with occasional stirring. Aftercooling, the mixture is washed with ether. Melting point 188 C.

PREPARATION II Sodium bromo-acetate g.) and 4-hydroxy-butanel-sulphonicacid sultone (100 g.) are heated for six hours at 150 C. upon anoil-bath and with occasional stirring. After coolin" the mixture isground in a mortar and thoroughly washed with ether. Melting point 200C.

PREPARATION III Bromo-Acezoxy-Illethane Sulphonic Acid Sodium Salt BrCHCOOCH SO Na Bromo-acetanhydride (21 g.) and sodium-hydroxymethanesulphonate (5.36 g.) are gently heated over a fiame until at about 60 C.the reaction sets in. At this moment, the flame is removed and thetemperature increases to about C. When the reaction diminishes inintensity the mass is heated for some minutes at C. After cooling, thereaction product is washed out with ether and purified byrecrystallization from diluted ethanol or propanol. Melting point 243 C.(with decomposition).

The quaternary salts employed in the present invention can also beobtained by treating the corresponding quaternary salt, bearing at thenitrogen atom an organic residue of the following constitution:

wherein A has the same significance as set forth hereinbefore, and whichmay be prepared by treating the corresponding heterocyclic base with acompound of the general formula:

wherein X and A have the same significance as set forth hereinbefore,with a compound of the general formula:

wherein B represents a hydrocarbon radical containing a straight carbonchain of at least three carbon atoms.

As suitable heterocyclic nitrogen bases, known to be convertible into amethine dyestuif, may be mentioned the heterocyclic nitrogen basescontaining in the alpha or gamma-position to the nitrogen atom of theheterocyclic ring an alkyl, thioalkyl, beta-alkylthiovinyl,betahalogenovinyl, beta (N-methylanilino)-vinyl or beta-acylanilidovinylgroup, which vinyl groups may carry a substituent, such as a lower alkylgroup.

While the process of preparing the quaternary halides is subject tovariation particularly in respect of the nature of the heterocyclicnitrogen bases, the nature of the compounds of the general Formula Iabove, the proportions of the reactants, the temperature, the time ofreaction and the methods of isolation and purification of the quaternaryhalides, the following examples will serve to illustrate the method forpreparing the quaternary halides.

PREPARATION rv 2-Methyl-3-(Sodium. Sulpho-Carbomethoxy-Methyl-Benzothiazolium Bromide Br orrio-acetoxymethane sulphonic acid sodiumsalt (3 .g.) and Z-methyl henzothiazole g.) are heated for eight hoursat 105 C. and at times the mass is thoroughly stirred. After cooling themixture is washed with ether. The product is very hygroscopic.

PREPARATION V 2-Methyl-3-(Omega Sodium Sulpho-Carbopropoxy- Methyl)-Benzothiaz0lium Bromide 3-bromo-"lcetoxy-propane-l-sulphonic acidsodium salt (28.3 g.) and Z-methyl benzothiazole (20 g.) are heated forsixteen hours at 100 C. After cooling, the product is Washed with ether.Melting point: 172 C.

PREPARATION VI 2-Methyl-3-(Omega-Sodium Sulpho-Carbobutoxy- Methyl)-Benz0thiaz0lium Bromide OH3 Ni GHQ-C O 0-OHg-C HzOHzGHgS 03Na A mixtureof 4-bromo-acetoXy-hutane-1-sulphonic acid sodium salt (75 g.) and2-methyl-benzothiazo1e (65 g.) is heated for 22 hours at 100 C. Themixture is thoroughly stirred from time to time and after cooling theresulting product is Washed With ether. Mel-ting point: 190 C.

PREPARATION VII 2-Methyl-3-(Omega-Sodium Sulpho-Carbobutoxy- Methyl)-Benz0selenaz0lium Bromide S e L0H. g/

A mixture of Z-methylbenzoselenazole (30 g.) and 4- bromQ-acetOXybutane-I-sulphonic acid sodium salt (30 g), is heated for 18 hours at100 C. After cooling, the reaction mixture is ground in a mortar andwashed With ether. Melting point: 168 C.

PREPARATION VIII 2-Methyl-3-(Omega-Sodium Sulpho-Carbopropoxy- Methyl)-Benz0seleziaz0lium. Bromide C-CH g B-bromo-acetoxy-propane-l-sulphonicacid sodium salt (28.3 g.) and Z-methyl-benzoselenazole (25 g.) areheated for twenty hours at 110 C. upon an oil-bath and after coolingWashed with ether. Melting point: 170 C.

0 PREPARATION 1X 2-Metlzyl-3-(Omega-Sodium-Sulph0-Carb0butoxy-Melhyl)-Thiazolinium Bromide H o-s H2 C-CHs N+ H2-O O OCH2GHzCHgCH2-SON3 2-methyl-thiazoline (20.2 g.) and 4-hromo-acetoxybut-ane-1-sulphonicacid sodium salt (29.7 g.) are heated for six hours at C. and aftercooling the reaction product is ground and Washed With ether. Meltingpoint: 162 C.

PREPARATION XI 2 -MeIhyl-3- Omega-SodiumeSulpho-Carbopropoxy- Methyl)-6-Meth0xy-Benzothiazolium Bromide H 0 0- T C H2C 0 OCH2 CH2 CH2 SO3NELA mixture of 2-rnethyl-6-methoxy-benzothiazole (24 g.) and3-brorno-acetoxy-prop ane-l-sulphonic acid sodium salt (28.3 g.) isheated for sixteen hours at 100 C. After cooling the reaction product iswashed with ether. Melting point: 180 C.

PREPARATION XII 2-Methyl-3-(Omega-S0dium Sulpho-Carbobutoxy-Methyl)-6-Methoxy-Benzothiazolium Bromide HgCO- --S Hz-COO-CHzCHg-CHgCHg-SO3NL 2-methyl-6-rnethoxy-floenzothiazole (18 g.) and4-b-romo-acetoxy-butane-l-sulphonic acid sodium salt (23.7 g.) areheated for sixteen hours at 100 C. After cooling the reaction product isground and washed with ether. Melting point: C.

PREPARATION XIII 2-Methyl-3-(Omega-Sodium Sulpho-Carbopropoxy-Methyl)-6-Methyl Benzothiazolium Bromide A mixture of2,6-dimethyl-benzothiazole (22 g.) and 3-bromo-acetoxy-propane lsulphonic acid sodium salts (28.3 g.) is heated for sixteen hours at 100C. Aft r cooling, the resulting product is thoroughly washed with ether.Melting point: 172 C.

7 PREPARATION XIV 2-Metlzyl-3-(Omega-Sodium Sulpho-Carbobutoxy-Methyl)-6-Methyl-Benzotlziazolium Bromide H3O- T A mixture of2,6-dimethy1-benzothiazole (20 g.) and 4-bromo-acetoxy-butane-1-su1phonic acid sodium salt (29.7 g.) is heatedfor sixteen hours at 100 C. After cooling the product obtained is washedwith ether. Melting point: 174 C.

PREPARATION XV 2-114 ethy l-3 Om ega-S odi um S ulpho-Carb obutoxy-Methyl)-5,6-Dimethyl-Benzothiazolizun Bromide d-OH2,5,6-trimethyl-benzothiazole 17.5 g.) and4-bromoacetoxybutane-l-sulphonic acid sodium salt (21.5 g.) are heatedtogether for sixteen hours at 100 C. After cooling, the quaternary saltobtained is ground and Washed with ether. Melting point: 180 C.

PREPARATION XVI 2-Methyl-3-(Omega-Sodium Sulpho-Carbobutoxy-Methyl)-Benzoxazolium Bromide I'IgC O CH2CHg-CH2CH3SO3NQZ-methyl-benzoxazole (25 g.) and 4-bromo-acetoxybutane-l-sulphonic acidsodium salt (29 g.) are heated for sixteen hours at 130 C. After coolingthe viscous reaction product solidifies by washing with ether. Theproduct is very hygroscopic.

PREPARATION XVII 2-M ethyl-3 Om ega-S odium S ul pho-Carbobutoxy- Methyl-5-Phenyl-Benzoxazolium Bromide Z-methyl-S-phenyl-benzoxazole g.) and4-br0moacetoxy-butane-l-sulphonic acid sodium salt (29.7 g.) are heatedfor sixteen hours at 130 C. After cooling and washing with ether thesticky mass solidifies. The product is very hygroscopic.

PREPARATION XVIII 2-Methyl-3-(Omega-Sodium Suiplzo-Carbobutoxy- M ethyl-6-M ethoxy-Benzoxazolium Bromide 2-methyl-6-methoxy-benzoxazole (20 g.)and 4-bromoacetoxy-butane-l-sulphonic acid sodium salt (29 g.) areheated for sixteen hours at 100 C. After cooling the reaction product iswashed with ether. The product is very hygroscopic.

a PREPARATION XIX 2-Methyl-3- [p- Omega-Sodium S ulpho-CarbobutoxyBenzyl] -Benzothiazolium Bromide PREPARATION XX 2,5 -Dimethyl-3- (Sodium S ulpho-Carbomethoxy-M ethyl Benzothiazolium Bromide A mixtureconsisting of 2,S-dimethyl-benzothiazole (4.5) g.) and sodiumsulpho-carbomethoxy-methyl bromide (6 g.) is heated for 24 hours at C.in a drying oven. The product is washed with ether, ground, sucked offand dried in vacuum.

PREPARATION XXI 2,6-Dimethyl-3-(Sodium-Sul iIzo-Carbomethoxy-Methyl)-Benzothiazolium Bromide CH Z (IJII2C O O-GHg-S O3N8 A mixture consistingof 2,6-dimethylbenzothiazole (4.5 g.) and sodiumsulpho-carbomethoxymethyl bromide (6 g.) is heated for 24 hours at 110C. in a drying oven.

The product obtained is washed with ether, ground and sucked oft.Melting point: 178 C.

PREPARATION XXII 1 -Eihyl-2-Methyl-3- (Sodium S ulplzo-C arbomet/loxy- Methyl -5 ,6 -Diclz loro-Benzimz'dazoli um Bromide CH; i/

CH2 O O OCI'Ig-S O Na 1-ethyl-2-methyl-5,6-dichlorobenzimidazole (7 g.)and bromo-acetoxymethane sulphonic acid sodium salt 4.45 g.) are heatedfor 24 hours at 110 C., chilled and washed twice with acetone (10 cm?)and once with ether (10 cm.

PREPARATION XXIII 2,4-Dimethyl-3-(Sodium Sulpho-Carbomethoxy-Methyl)-Thiazolium Bromide HO HaC-ii 2,4-dimethy1thiazole (8 g.) andbromo-acetoxymethane sulphonic acid sodium salt (7.65 g.) are heated for18 hours at 110 C., chilled and washed with ether.

As stated hereinbefore, the new methine dyestufis according to thepresent invention may be obtained starting from the new heterocyclicquaternary salts by application of the usual condensation methods knownto those skilled in thevart.

The following description of some methods for preparing the new methinedyes is not complete and therefore is not to be regarded as limiting thescope of our invention but merely as a survey of the most usualcondensation methods.

The new asymmetric cyanine dyes according to the present invention canbe prepared by condensing a cycloammonium quaternary salt of thefollowing general formula:

l l MOgS-B-O-C -AI =orron) ape-011311? H wherein Z represents thenon-metallic atoms to complete a heterocyclic nucleus containing to 6atoms in the 'heterocyclic ring of the type known in cyanine dyes, suchas those selected from the group consisting of those of the thiazoleseries (e.g. thiazole, 4-methylthiazole, 4-phenyl thiazole,5-methylthiazole, S-phenylthiazole, 4,5-dimethylthiazole,4.5-CliPhEi1Yl-4Zhifi20lfi, 4-(2-thienyl)-thiazole, etc), those of thebenzothiaaole series (e.g. benzothiazole, 4- chlorobenzothiazole,S-chlorobenzothiazole, 6-chloroben- Zothiazole, 7-chlorobenzothiazole,4-rnethylbenzothiazole, S-methylbenzothiazole, 6-methylbenzothiazole,5-bromo benzothiazole, 6-bromobenzothiazole, 4-phenyl-benzothiazole,S-phenylbenzothiazole, 4-methoxybenzothiazole, 5- methoxybenzothiazole,dmethoxybenzothiazole, S-iodobenzothiazole, 6iodobenzothiazole,4-ethoxybenzothiazole, S-ethoxybenzothiazole,4,5,6,7-tetrahydrohenzothiazole, 5,G-dimethoxybenzothiazole,5,6-dioxymethylenebenzothiazole, S-hydroxybenzothiazole,6-hydroxybenzothiazole, 5,ddimethylbenzothiazole), those of thenapththothiazole series (e.g. naphtho[2,l-d]thiazole, naphtho[l,2-d]thiazole, S-methoxynaphtho[1,2-d]thiazole, S-ethoxynaphtho[l,2d]ithiazole, 8 rnethoxynaphtho [2,l-d]thia zole, 7-methoxyn-aphtho[2,1-d1thiazole), those of the thionaphtheno[7,6'-d]thiazole series(e.g. 4-me-thoxythio naphtheno [7',6-d]thiazole), those of the oxazoleseries (eg. 4-methyloxazole, 5-methyloxazole, 4-phenyloxazole,4,5-diphenyloxazole, 4-ethyloxazole, 4,5-dimethyloxazole,S-phenyloxazole), those of the 'benzoxazole series (e.g. benzoxazole,S-chlorobenzoxazole, S-methylbenzoxazole, S-phenylbenzoxazole,6-methylbenzoxazole, 5,6-dimethylbcnzoxazole, 4,6-dimethylbenzoxazole,S-methoxybenzoxazole, 6-methoxybenzoxazole, S-hydroxybenzoxazole, 6-hydroXy-benzoxazole), those of the naphthoxazole series (e.g.naphtho[2,l-d]oxazole, naphtho[1,2-d]oxazole), those of the selenazoleseries (e.g. 4-methylselenazole, 4- phenylselenazole), those of thebenzoselenazole series (e.g. benzoselenazole, 5-chlorobenzoselenazole,S-methoxybenzoselenazole, 5-hydroxybenzoselenazole,4,5,'6,7-tetrahydrobenzoselenazole), those of the naphthoselenazoleseries (e.g. naphtha 2,1-d selenazole, naphtho 1,2-d Selenazole), thoseof the thiazoline series (e.g. thiazoline, 4-1nethylthiazoline,4-hydroxymethyl-4-methylthiazoline, 4,4-bishydnoxymethylthiazoline,4-acetoxyrnethyl-4-rnethylthiazoline, 4,4 bis-acetoxymethylthiazoline),those of the t iazolidine series (e.g.2-benzothiazolylidene-4-thi-azolidone), those of the oxazoline series(eg. oxazoline, 4--hydroxymethyl 4 methyloxazoline, 4,4 bishydroxyrnethyloxazoline, 4-acetoxymethyl-4-methyloxazoline,4,4-bisacetoxymethyloxazoline), those of the oxazolidine series, thoseof the selenazoline series (e.g. selenazoline), those of the,Z-quinoline series (e.g. the quinoline, 3-methylquinoline,S-methylquinoline, 7-methylquinoline, 8-methylquinoline,o-chlonoquinoline, S-chloroquinoline, 6 -methoxyquinoline,6-ethoxyquinoline, 6-hydroxyquinoline, 8-

1O hydroxyquinoline etc.), those of the 4-quin0line series (e.g.quinoline, 6-methoxyquinoline, 7-methylquinoline, 8- methylquinoline),those of the l-isoquinoline series (eg. isoquinoline,3,4-dihydroisoquinoline), those of the 3-isoquinoline series (e.g.isoquinoline), those of the 3,3-dialkylindolenine series (eg.3,3-dirnethylindolenine, 3,3,5- trimethylinodolenine,3,3,7-trin1ethylindolenine), those of the pyridine series (e.g.pyridine, S-methylpyridine), those of the benzimidazole series (e.g.l-ethylbenzimidazole, 1- phenylbenzimidazole,1-ethyl5,6-dichlorohenzimidazole,1-hydroxyethyl-5,6-dichlorobenzimidazole, l-ethyl-S-chlorobenzimidazole,1ethyl-5,6-di'bromohenzirnidazole, 1-ethyl-5-chloro-6-aminobenzimidazole, l-ethyl-S-chloro-G-bromobenzimidazole, l-ethyl-5-phenylbenzimidazole, lethyl 5fluorobenzimidazole, l ethyl 5 cyanobenzimidazole,1-(/3-acetoxyethyD-S-cyanobenzimidazole, 1- ethyl-5-chloro-6cyanobenzimidazole, l-ethyl-S-fiuoro-ficyano benzimidazole,1-ethyl-S-acetyl-benzimidazole, 1- ethyl-5-chloro-6-fiuorobenzimidazole,l-ethyl-S-carboxy- 'benzimidazole, 1-ethyl-7-carboxybenzimidazole,l-ethyl-S- carbethoxyhenzimidazole, 1-ethyl-7-carbethoxybenzimidazole,1-ethyl-S-sulphonarnidobenzimidazole, l-ethyl-S-N-ethylsulphonamidobenzimidazole; X represents an acid radical of the typeused in the cyanine dyes, such as chloride, bromide, iodide,perchlorate, benzenesulphonate, ptolusulphonate, methylsulphate,ethylsulphate etc.;

It represents 1 or 2 and M, B and A have the same significance as setforth hereinbefore,

with a cyclammoniurn quaternary salt represented by the followingFormula HI:

wherein:

R represents an alkyl group of the formula C H wherein r represents apositive integer from 1 to 4 such as methyl, ethyl, propyl, isopropyl,butyl, isobutyl, an unsaturated aliphatic radical such as aliyl, ahydroxy substituted alkyl radical such as ,B-hydroxyethyl, an aralkylradical such as benzyl, a substituted aralkyl radical such as carboxybenzyl, a mononuclear aryl group such as phenyl, a substitutedmononuclear aryl group such as carboxyphenyl, or a radical of theformula as described above.

Z represents the non-metallic atoms to complete a heterocyclic nucleuscontaining 5 to 6 atoms in the heterocyclic ring such as those describedfor Z,

11 represents 1 or 2,

X represents an acid residue as known in cyanine dyes and D representsan alkylmercapto, an arylmercapto, a betaarylaininovinyl, adelta-arylamino-1,3-butadienyl, a betaalkylmercaptovinyl, abeta-arylmercaptovinyl or a betaacetanilidovinyl group, which vinylgroups may carry a substituent, such as methyl, benzyl or phenyl.

The condensations are advantageously carried out in the presence of abasic condensing agent, for example a trialkylamine such astriethylamine, a dialkylaniline, a heterocyclic tertiary amine such aspyridine, N-alkylpiperidine or the like.

The new symmetrical cyanine dyes according to the present invention canbe prepared by condensing a cyclammonium quaternary salt represented bythe general Formula II above with an ortho car boxylic acid alkyl ester,such as ethyl ortho-formate and ethyl ortho-acetate, advantageously inthe presence of a carboxylic acid anhydride, for example aceticanhydride.

The new cyclammonium quaternary salts represented by the general FormulaII above can further be condensed with a compound represented by thefollowing formula:

t represents an integer from 1 to 3, Ar represents an aryl group and Land L each represents a methine group.

The aryl-amino-vinyl intermediates, or vinylene homologues thereof thusobtained can be transformed into the corresponding acetarylidoderivatives by boiling with acetic anhydride, which can be condensed tounsymmetrical cyanine dyes with cyclammonium quaternary salts containinga methyl group in alpha or gamma position to the nitrogen atom. Thecondensations are advantageously carried out in the presence of a basiccondensing agent as set forth above.

The most valuable methine dyes of the present invention may berepresented by one of the two general Formulae A and B:

E -z' m n E --Z Z" and Z each represents the non-metallic atom necessaryto complete a heterocyclic nitrogen nucleus of the type contained incyanine dyes,

n and n each represents a positive integer from 1 to 2,

! represents a positive integer from 1 to 3,

R represents a member selected from the group consisting of a hydrogenatom, and lower alkyl radical,

X represents an acid radical of the type used in cyanine dyes,

R represents a radical of the type contained in cyanine dyes assubstituent on the cyanine nitrogen atom,

R represents a radical of the formula in said radicals, R and R' 2representing a positive integer from 1 to 6, M representing an alkalimetal atom or cation such as ammonium and A representing a memberselected from the group consisting of a lower alkylene radical or anarylene alkylene radical such as a benzylene radical.

The following examples will serve to illustrate further the manner ofobtaining our new methine dyes.

EXAMPLE 1 The dyestuff anhydro- [2- (ethyl-benzothiazole) ]-{2- 3-(sulpho carbomethoxy methyl) benzothiazole]}mesomethyl-trimethinecyanine hydroxide, having the formula:

is prepared as follows:

2-methyl-3-(sodiurn sulpho-carbomethoxy-methyl) -benzothiazolium bromide(2 g.) and Z-(fl-methyl-B-methylis prepared as follows:

2-methyl-3-(omega-sodium sulpho-carbopropoxymethyl)-benzothiazoliumbromide (8.65 g.) and Z-(B-acetanilido-vinyl)-3-ethylselenazolium iodide(9 g.) are dissolved in 100 cm. methanol. After cooling the solution at0 C., 5.6 cm. triethylamine are added drop by drop and after one hourstirring under ice cooling the dyestutf is sucked off and recrystallizedthree times from ethanol. Absorption maximum: 506 mg.

A silver chloride emulsion containing per kg. 20 mg. of this dyestuff issensitized to 5 mg with a broad maximum at 540545 mg.

EXAMPLE 3 The dycstutf anhydro- 2- 3-ethyl-benzoselcneazole) {2 [3(omega ulpho carbopropoxymethyl)-benzoselenenazole]}-mesomethyl-trimethinecyanine hydroxide,having the formula:

is prepared as follows:

2-methyl-3-(omega-sodium sulpho-carbopropoxy-methyl)-benzo selenazoliumbromide (4.8 g.) and Z-(fl-methyl-fl-methylmercapto-vinyl) 3ethyl-benzoselenazolium methylsulphate (4.1 g.) are dissolved in amixture of 20 0111. methanol and 20 cm. pyridine. After adding drop bydrop 1.4 cm. triethylamine, the solution is brought to boilingtemperature for five minutes. The dyestuif is precipitated with etherand purified by recrystallization from ethanol and methanol. Absorptionmaximum: 563 Ill/L.

A silver bromo-iodide emulsion containing per kg. 15 mg. of thisdyestuif is sensitized to 655 ITLLL With a broad maximum at 600 111 1..

EXAMPLE 4 The dyestulf anhydro-[2-(3-ethyl-thiazoline) ]-{2-[3- (omegasulpho carbobutoxy methyD-benzothiazole] trimethinecyanine hydroxide,having the formula:

is prepared as follows:

2-methy1-3-(omega-s0dium sulpho-carbobutoxymethyl)- benzothiazoliumbromide (4.60 g.) and 2-(/3-acetanilidovinyl)-3-ethylthiazoliniun1bromide (3.55 g.) are dissolved in Warm ethanol (50 cm?) and aftercooling the solution 13 at C., 1.4 cm. trimethylamine are added. Afterstirring one hour under ice cooling, the dyestutf is sucked off andrecrystallized from ethanol. Absorption maximum: 504 mp.

A silver chloride emulsion containing per kg. 20 mg. of this dyestutf issensitized to 580 m with a maximum at .530 III/1..

EXAMPLE The dyestutf anhydro-[2-(3-methyl-naphtho-l':2:'4:5-thiaZole)]-{2-[3-(omega sulpho carbobutoxy-methyl)- benzothiazolc]}-monomethinecyanine hydroxide, having the formula:

is prepared as follows:

2-methyl-3-(omega-sodium-sulpho carbobutoxy-methyl)-benzothiazoliumbromide (4.5 g.) and 2-methylmercapto-3 -methyl-naphtho-l :2 :4S-thiazolium methyl sulphate (3.6 g.) are dissolved in methanol (30cmfi) and after cooling at 0 C., 2.8 cm. triethylamine are added. Afterstirring for three hours at this temperature, the dyestuif is sucked offand recrystallized from diluted ethanol. Absorption maximum: 442 m w Asilver chloride emulsion containing per kg. 20 mg. of this dyestuff isstrongly sensitized to 500 m with a sharp maximum at 470 mp.

EXAMPLE 6 The dyestutf anhydro-[2-(3-ethylsbenzothiazole)]-{2- [3 (omegasulpho carbobutoxy methyl)-5-benzoxazole]}-trimethinecyanine hydroxide,having the formula:

is prepared as follows:

2-ethyl-3-(omega-sodium sulpho carbobutoxy-methyl)-5-phenylbenzoxazolium bromide '(5 .06 g.) and Z-(B-acetanilidovinyl-3-ethyl-benzothiazolium iodide (4.50 g.) are dissolvedin 50 cm. ethanol and after cooling the solution at 0 C., 1.4 cm.triethylamine are added whilst stirring. After one hour the dyestuff isprecipitated with ether and recrystallized three times from ethanol.Absorption maximum: 526 m A silver bromide emulsion containing per kg.30 mg. of this dyestuff is strongly sensitized to 600 m with a highmaximum at 550 mp EXAMPLE 7 The dyestuifanhydro-[2-(3-ethyl-benzoxazole)]-{2-[3- (omega-sulpho carbobutoxymethyl)-6-methoxy-benzothiazole]}-trimethinecyanine hydroxide, havingthe formula:

is prepared as follows:

2-methyl-3-(omega-sodium sulpho-carbobutoxy-methyl)-6-methoxybenzothiazolium bromide (4.76 g.) and 2- (B-acetanilidovinyl)-3-ethylbenzoxazolium iodide (4.34 g.) are dissolved in ethanol (50 cm?) andafter cooling the solution at 0 C., 1.4 cm. triethylamine are added dropby drop whilst stirring. After standing for two hours the dyestuif iscompletely precipitated with ether and recrystallized three times fromethanol. Absorption maximum: 530 mm.

A silver .bromide emulsion containing per kg. 30 mg. of this dyestuff issensitized to 600 m with a maximum at 500 my" EXAMPLE 8 The dyestuffanhydro-bis{2-{3-(omega-sulpho-carbobutoxymethyl -benzoxazole]}-trimethinecyanine hydroxide, having the formula:

2-methyl-3-(omega-sodiumsulpho-carbobutoxy-methyl)-5,6-dimethyl-benzothiazolium bromide (4.74g.) orthoethyl formate (2.96 g.) and acetic anhydride (25 cmfi) areheated for fifteen minutes at boiling temperature. After cooling, thedyestuif crystallizes and is purified by recrystallizing three timesfrom methanol. Absorption maximum: 570 m A silver bromo iodide emulsioncontaining per kg. 25 mg. of this dyestuif is sensitized to 670 m with amaximum at 590 mp EXAMPLE 10 The dyestuff anhydro-(3-n-propyl-thiazoline) {2- [3- (sulpho carbomethoxy methyl)benzothiazole] }-trimethinecyanine hydroxide, having the formula:

is prepared as follows:

2methyl-3-(sodium sulpho carbomethoxy-methyl)- v benzothiazolium bromide(4 g.) is dissolved in methanol (25 cm. After addition ofZ-(B-acetanilidovinyl)-3- propyl-thiazolinium iodide (4.9 g.) andtriethylamine (2.8 cmfi), the solution is cooled at 0 C. for ninetyminutes. The dyestuif is sucked off and recrystallized from a mixtureethanol-water. Absorption maximum: 504 m A silver chloride emulsioncontaining per kg. 20 mg. of this dyestuif is sensitized to 575 mg witha maximum at 530 III/1..

EXAMPLE 11 The dyestuif anhydro-[2-(3-ethylthiazoline)]-{2-[3- 16(sulpho carbomethoxy-rnethyl) 5 methyl-benzothiasucked off andcrystallized from ethanol. Absorption zole]}-trirnethinecyaninehydroxide, having the formula: maximum: 506 me.

A silver chloride emulsion containing per kg. mg. -T S CH2 of thisdyestuff is sensitized to 600 mg with a maximum 12 540 Into. o-on=orrcn=d n 5 a y 1I3C- \N 1 N 1 DxAMPLD 14 I p The dyestuif anhydro{2 [3sulpho carhomethoxy- CHPCOOCHE 803 [5 (3 ethylrhodanine) 2] {2 [3p-(ornega-sulphois prepared as follows: carbobutoxy) benzylbenzthiazoleJ} alpha benzyl di- 2,5-dimethyl-3-(sodiumsulpho-carbomethoxymethyl)- 10 methine rhodacyanine hydroxide, havingthe formula:

(:JHt =0 o=t 3-s \N/ 0:0 d-cn:

an. f N

(2 115 rim-O-coownm-sw benzothiazolium bromide (4.2 g.) andZ-(fi-acetanilidois prepared as follows: vinyl)-3-ethyl thiazoliniumbromide (3.5 g.) are dissolved [2-(3-ethyl-benzothiazole)]-[5 (3ethylrhodanine)]- in methanol (25 cm?) and the solution is cooled at 0C. a-benzy1-dimethine merocyanine methyl para tolusul- 2.8 cm.triethylamine are added drop by drop and after phonate (3.1 g.) and2-methyl-3-[p-(omega-sulphoone hour stirring under ice-cooling thedyestuif is sucked carbobutoxy) benzyl]-benzothiazo1ium bromide (2.6 g.)off and recrystallized three times from a mixture ethanolare dissolvedin ethanol (25 cm?) and after adding triwater. Absorption maximum: 508 methylamine (1.4 cm?) boiled for fifteen minutes. After A silver chlorideemulsion containing per kg. 15 mg. cooling, the dyestuff is precipitatedwith water and reof this dyestuff is sensitized to 590 m with a broadmaxicrystallized three times from diacetone alcohol. Absorpmum at 540mg. tion maximum: 610 mg.

EXAMPLE 12 A silver bromo-iodide emulsion containing per kg. 30 Thedyestuff anhydm [z (3 ethylthiazoline)1 mg. of this dyestulf issensitized to 690 my. with a broad (sulpho-carbomethoxy methyl) 6methylbenzothiamaxlmum $650111!- zole]}trimethinecyanine hydroxide,having the formula: EXAMPLE 15 The dyestulfanhydro-[2-(3-ethyl-naphtho-1':2'z4:5- H30 S CHZ thiazole)] {2[3-(omega-sulpho-carbobutoxy)-methy1- Hz benzselenazole1}trimethmecyanme hydroxlde, having the \Ny formula.

N are 0 o CH -S 03- (lhHs l i is prepared as follows: y *CH:CH CH:2,6-dimethyl 3-(sodiumsulpho-carbomethoxy-methyl)- N t benzothiazoliumbromide (4.2 g.) and Z-(fi-acetanilidoz Hz)i a- 52115 Ivinyl)-3-ethylthiazolinium bromide (3.5 g.) are dissolved in methanol(35 cm?) and the solution is cooled at 0 C. 2.8 cm. triethylamine areadded drop by drop and after Prepared as follows: one hour stirringunder ice-cooling the dyestutf is sucked 2 methyl 3 (omeg? sulphocarbobutoxy" oif and recrystallized three times from a mixture ethano1methyi)fberlzoselenazohum bromlde f 3" Water Absorption maximum; 506 macetanilidovinyl)-3-ethylnaphtho 1 :2 14:5 thiazolium- A Silver chlorideemulsion containing per kg 15 mg r para-tolusulphonate (5.5 g.) aredissolved in acet1c anof this dyestuff is sensitized to 590 m with abroad maxi- 3- and afidlng drop by P mum at 535 m cm. trietnylamine thesolution is brought at boiling tem- EYAMPLE 13 perature for twentym1nutes. After cooling, the dyestuif precipitates and is recrystallizedfrom ethanol. Absorp- The dyestuff anhydro-[2-(3-ethylth1azol1ne)] 2-{3-[p i i 5 4 mm m ga sulpho Ca Y) y benZOthlaZOle} A silver bromoiodide emulsion containing per kg. 15

trimethinecyanine hydroxide, having the formula: mg. of this dyestulf issensitized to 690 mg with a broad maximum at 635-640 III/L. s S CH2EXAMPLE l6 B H2 The dyestulfanhydro{2-[1-ethyl-3-(sulphocarbomethoxy-methyl) 5,6dichlorobenzimidazole]}[2-(3-ethyl- I O O O (OHDFSOQH zHsaglriliolrlrgzolefl trimethmecyanme hydroxide, having the is prepared asfollows: C1 0 Zmethyl 3 [p (omega sodium sulpho carbobutoxy) Cl C CH:CHOH=(|J benzyl]-benzothiazoliurn bromide (5.2 g.) andZ-(p-acetanilidovinyD-S-ethyl thiazolinium bromide (3.5 g.) are \N+ Ndissolved in ethanol (35 cm?) and after cooling the CI'IT COOOH:Z SO3(Jim solution at 0 C., 2.8 cm. triethylamine are added. After i prepareda follow stirring for one hour under ice-cooling the dyestufl is1-ethyl-2-methyl-3-(sodium sulpho-carbomethoxy- 17methyl)-5,6-dichlorobenzimidazolium bromide (2.4 g.) and Z-(phenyliminoethylidene) 3 ethylbenzoxazoline (1.65 g.) are dissolved in aceticanhydride (20 0111. and, after the addition of triethylamine (1.4 cm?)left overnight at 20. The dyestuii' is precipitated with ether andrecrystallized twice from ethanol and once from diacetone alcohol-water.Absorption maximum: 491 mu.

EXAMPLE 17 The dyestufl? anhydro{2 [3 sulphocarbornethoxymethyl)-4-methylthiazole]}[2 (3 ethylbenzoxazole)]trimethinecyanine hydroxide, having the formula:

is prepared as follows:

2,4-dimethyl-3-(sodium sulpho-carbomethoxy-methyl)- thiazolium bromide(1.8 g.) and Z-(B-acetanilidovinyD- 3-ethylbenzoxazolium iodide (2.2 g.)are dissolved in acetic anhydride (2O cm. triethylamine (1.4 cm?) isadded and the mixture is heated for 2 hours at 80. After cooling thedyestuff is precipitated with ether and recrystallized three times fromethanol. Absorption maximum: 518 m As shown in the above examples, thenew methine dyes spectrally sensitizes photographic silver halideemulsions when incorporated therein. Although the new methine dyes areuseful especially for extending the spectral sensitivity of thecustomarily employed gelatino silver chloride, gelatino silverchloro-bromide, gelatin silver bromide, gelatino silver bromoidine andgelatin'o silver chloro-bromo-iodine emulsions, photographic emulsionscontaining water-permeable colloids other than gelatin, such asagar-agar, zeine, collodion, water-soluble cellulose derivatives,polyvinyl alcohol or other hydrophilic synthetic or natural resins orpolymeric compounds, may equally well be sensitized according to thepresent invention.

To prepare photographic emulsions sensitized according to the inventionwith one or more of the new methine dyes, the dye, or dyes can beincorporated in the photographic emulsion by one of the methodscustomarily employed in the art. In practice, it is convenient to addthe dyes to the emulsion in the form of a solution in an appropriatesolvent. The dyes are advantageously incorporated in the finished,washed emulsions and should be uniformly distributed throughout theemulsion. The concentration of the dyes in the emulsion can vary widely,for example from 1 to 100 mg. per kg. of flowable emulsion and will varyaccording to the effect desired. The suitable and most economicalconcentration for any given emulsion will be apparent to those skilledin the art, upon making the ordinary tests and observations customarilyused in the art of emulsion making.

The new methine dyes can be incorporated in photographic emulsions thegeneral sensitivity of which has been increased by physical and chemicalripening. An suitable chemical sensitizers may be mentioned the wellknown sulphur sensitizers such as allylisothiocyanate, allylthiourea,sodium thiosulphate, potassium selenocyanide and the natural sensitizersoriginating in the gelatin, reducing sensitizers such as theimino-aminomethanesulphinic acid and the derivatives thereof, and thesalts of noble metals such as gold, platinum and palladium.

The photographic emulsions optically sensitized ac cording to theinvention may further be supersensitized and/ or hypersensitized by oneof the methods known to those skilled in the art.

In preparing the photographic emulsions according to the invention, theusual addenda such as antifogging agents, stabilizers, anti-bronzingagents, hardeners, wetting agents, plasticizers, developmentaccelerators, color couplers, fluorescent brighteners and ultra-violetscreening compounds can moreover be incorporated in the emulsion in themanner customarily employed in the art. In this respect it may bementioned that the sensitivity of the silver halide emulsions sensitizedaccording to the process of the present invention is not adverselyaffected but rather enhanced by the presence therein of certainfluorescent compounds. Another advantage of the process for sensitizingsilver halide emulsions according to the present invention is thecompatibility of the new methine dyes with anionic wetting agents andwith color couplers which is of great importance in the application ofthe new methine dyes for sensitizing the silver halide emulsion of alight-sensitive element for color photography.

Emulsions sensitized with the new methine dyes can be coated in theusual manner on a suitable support such as glass, cellulose derivativefilm, resin film or paper.

We claim:

1. A methine dye of the formula:

wherein:

Z constitutes the atoms necessary to complete a heterocyclic systemselected from the group consisting of benzothiazole, 6methoxybenzothiazole, 6 methyl benzothiazole, S-methyl benzothiazole,5,6-dimethyl benzothiozole, benzoselenazole, benzoxazole, S-phenylbenzoxazole, 6-methoxybenzoxazole, benzimidazole,5,6-dichlorobenzimadazole, thiazole and 4- methyl thiazole;

Z constitutes the atoms necessary to complete a heterocyclic systemselected from the group consisting of benzothiazole, benzoselenazole,benzoXazole, benzirnidazole, thiazole, naphthothiazole, selenazoline andthiazoline;

d is a positive integer from 1 to 3;

R is a member selected from the group consisting of hydrogen and methyl;

R is a radical of the formula wherein A is lower alkylene, p a positiveinteger from 1 to 6 and M an alkyl metal atom.

2. Methine dye of formula:

nroooontn-sw l 3. Methine dye of the formula:

1 4. Methine dye of the formula:

| s 2,213,995 CCH=OHCH=( J 6H. 5 2,646,430 \Zh/ 2,870,014 H COO(CH) -so2,892,836 a H 3 2,892,838

2,905,666 5. Methlne dye of the formula. 10 2,973,264

S S (L0H: 559,840 g/ 1H3 (SHQ COO (CHZ)A SO3 References Cited in thefile of this patent UNITED STATES PATENTS Riester et a1 Sept. 10, 1940Brooker et a1 July 21, 1953 Brooker et a1 Jan. 20, 1959 De Stevens June30, 1959 Sprague June 30, 1959 De Stevens Sept. 22, 1959 Nys et al Feb.28, 1961 FOREIGN PATENTS Belgium Feb. 5, 1958 OTHER REFERENCES Elsevier:Chemistry of Carbon Compounds, vol. IB, pages 809-10, ElsevierPublishing Co.,

Amsterdam (1952); QD 251 R 6.

1. A METHINE DYE OF THE FORMULA:
 2. METHINE DYE OF FORMULA: